Voltage converter and operating method of voltage converter

ABSTRACT

The voltage converter including an inductor connected between an output node and a switch node, a capacitor connected between the output node and a ground node, first transistor connected between the switch node and the ground node, a second transistor connected between the switch node and an input node, a boost capacitor connected between the switch node and a boost node, a first driver configured to drive a gate voltage of the first transistor based on a ground voltage of the ground node and a power supply voltage of a power node, a second driver configured to drive a gate voltage of the second transistor based on a switch voltage of the switch node and a boost voltage of the boost node and, and a regulator configured to control the boost voltage depending on a status of the voltage converter may be provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 to Korean PatentApplication No. 10-2017-0115348, filed on Sep. 8, 2017, in the KoreanIntellectual Property Office, the entire contents of which are herebyincorporated by reference.

BACKGROUND

Example embodiments of the inventive concepts disclosed herein relate tosemiconductor circuits, and more particularly, to voltage convertersand/or operating methods thereof.

A voltage converter is configured to convert a level of an input voltageand output the converted input voltage as an output voltage. The voltageconverter is used in various electronic devices. Generally, a supplyvoltage provided in a home, a company, or a public facility has a levelof 110 V or 220 V.

However, electronic devices usually use internal voltages having a levellower than 110 V or 220 V. To convert the supply voltage to internalvoltages, various voltage converters are used in an electronic device.Accordingly, there is an increasing demand for highly reliable voltageconverters to be used in various electronic devices.

SUMMARY

Some example embodiments of the inventive concepts provide voltageconverters with improved reliability and/or an operating methodsthereof.

According to an example embodiment, a voltage converter includes aninductor connected between an output node and a switch node, a capacitorconnected between the output node and a ground node, first transistorconnected between the switch node and the ground node, a secondtransistor connected between the switch node and an input node, a boostcapacitor connected between the switch node and a boost node, a firstdriver configured to drive a gate voltage of the first transistor basedon a ground voltage of the ground node and a power supply voltage of apower node, a second driver configured to drive a gate voltage of thesecond transistor based on a switch voltage of the switch node and aboost voltage of the boost node and, and a regulator configured tocontrol the boost voltage depending on a status of the voltageconverter.

According to an example embodiment, a voltage converter includes aninductor connected between an input node and a switch node, a firstcapacitor connected between the input node and a ground node, a firsttransistor connected between the switch node and the ground node, asecond transistor connected between the switch node and an output node,a boost capacitor connected between the switch node and a boost node, asecond capacitor connected between the output node and the ground node,a first driver that drives a gate voltage of the first transistor, asecond driver that drives a gate voltage of the second transistordepending on a boost voltage of the boost node and a switch voltage ofthe switch node, and a regulator configured to control the boost voltageby selecting one of two or more modes depending on a status of thevoltage converter.

According to an example embodiment, an operating method of a voltageconverter including first and second switching transistors includesdetermining a status of the voltage converter, and adjusting a gatevoltage to be applied to a gate of at least one switching transistor ofthe first and second switching transistors depending on the status ofthe voltage converter.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features will become apparent from thefollowing description with reference to the following figures, whereinlike reference numerals refer to like parts throughout the variousfigures unless otherwise specified, and wherein:

FIG. 1 illustrates a voltage converter according to an exampleembodiment of the inventive concepts;

FIG. 2 illustrates a voltage converter according to an exampleembodiment of the inventive concepts, for solving the above-describedissues;

FIG. 3 is a flowchart illustrating an operating method of the voltageconverter according to an example embodiment of the inventive concepts;

FIG. 4 is a block diagram illustrating a controller according to anexample embodiment of the inventive concepts;

FIG. 5 illustrates an example of a max duty detector according to anexample embodiment of the inventive concepts;

FIG. 6 illustrates an example in which a max duty detection signal isgenerated from a clock signal, an inverted clock signal, and a delayedclock signal;

FIG. 7 illustrates an example in which a second block generates a resetsignal as a pulse width of a first driving signal changes;

FIG. 8 illustrates an example in which a third block generates a setsignal as a pulse width of a first driving signal changes;

FIG. 9 illustrates an example of a boost voltage detector according toan example embodiment of the inventive concepts;

FIG. 10 illustrates an example of a regulation signal generatoraccording to an example embodiment of the inventive concepts;

FIG. 11 illustrates an example of a regulator according to an exampleembodiment of the inventive concepts;

FIG. 12 illustrates an example of signals associated with a regulationsignal generation block when a first signal and a second signal aredeactivated;

FIG. 13 illustrates how the regulator is controlled by signals of FIG.12;

FIG. 14 illustrates an example of signals associated with the regulationsignal generation block when a first signal is activated and a secondsignal are deactivated;

FIG. 15 illustrates how the regulator is controlled by signals of FIG.14;

FIG. 16 illustrates an example of signals associated with the regulationsignal generation block when a first signal is deactivated and a secondsignal are activated;

FIG. 17 illustrates how the regulator is controlled by signals of FIG.16; and

FIG. 18 illustrates a voltage converter according to an exampleembodiment of the inventive concepts.

DETAILED DESCRIPTION

Below, some example embodiments of the inventive concepts may bedescribed in detail and clearly to such an extent that an ordinary onein the art easily implements the inventive concepts.

FIG. 1 illustrates a voltage converter 10 according to an exampleembodiment of the inventive concepts. Referring to FIG. 1, the voltageconverter 10 includes first and second transistors 12 and 13, first andsecond gate drivers 14 and 15, a level shifter 16, a diode 17, acontroller 18, an output capacitor COUT, an inductor “L”, and a boostcapacitor CBST.

The voltage converter 10 may convert an input voltage VIN of an inputnode NIN to an output voltage VOUT of an output node NOUT. For example,the voltage converter 10 may be a buck converter that steps down a levelof the input voltage VIN to output the output voltage VOUT.

The first and second transistors 12 and 13 may be connected in seriesbetween a ground node GND supplied with a ground voltage and the inputnode NIN. A node between the first and second transistors 12 and 13 maybe a switch node NSW. The inductor “L” is connected between the switchnode NSW and the output node NOUT. The output capacitor COUT isconnected between the output node NOUT and the ground node GND.

The first gate driver 14 is biased by a power supply voltage VDD and theground voltage. The first gate driver 14 may output a first gate drivingsignal GD1 to control a gate of the first transistor 12. The second gatedriver 15 is biased by a boost voltage VBST of a boost node NBST and aswitch voltage VSW of the switch node NSW. The second gate driver 15 mayoutput a second gate driving signal GD2 to control a gate of the secondtransistor 13.

The controller 18 may receive a clock signal CLK and the output voltageVOUT. The controller 18 may control the first and second gate drivers 14and 15 in response to the clock signal CLK and the output voltage VOUT.A first driving signal DRV1 of the controller 18 is transmitted to thefirst gate driver 14.

A second driving signal DRV2 of the controller 18 is transmitted to thesecond gate driver 15 through the level shifter 16. The level shifter 16may convert (e.g., increase) a level of the second driving signal DRV2to a level defined by the boost voltage VBST and the switch voltage VSW.

The boost capacitor CBST is connected between the boost node NBST andthe switch node NSW. The power supply voltage VDD is transmitted to theboost capacitor CBST through the diode 17. When the first transistor 12is turned on, the boost capacitor CBST may be charged by the powersupply voltage VDD. The first and second transistors 12 and 13, thefirst and second gate drivers 14 and 15, the level shifter 16, the diode17, and the controller 18 may be implemented with a single chip 11.

When the first transistor 12 is turned off, the boost capacitor CBST maymaintain the boost voltage VBST to be higher, by an amount of thecharged voltage, than the switch voltage VSW. That is, the boostcapacitor CBST may control the boost voltage VBST for biasing the secondgate driver 15 to be greater than the switch voltage VSW, so as tooutput a level that allows the second gate driver 15 to turn on thesecond transistor 13.

However, some issues may occur in the voltage converter 10 illustratedin FIG. 1. For example, when the voltage converter 10 is powered on, theboost capacitor CBST may not be charged. That is, the boost voltage VBSTmay be the same as the switch voltage VSW, and the second gate drivingsignal GD2 of the second gate driver 15 may fail to turn on the secondtransistor 13. Accordingly, the voltage converter 10 may cause anabnormal operation.

The voltage converter 10 may enter a power saving mode or a sleep modeor may stop voltage conversion under control of an external device. Forexample, stopping of the voltage conversion is called a “pulse skip”.During the pulse skip, a voltage charged in the boost capacitor CBST maybe leaked out. Accordingly, the second gate driving signal GD2 may failto turn on the second transistor 13, thereby causing an abnormaloperation of the voltage converter 10.

The first gate driving signal GD1 and the second gate driving signal GD2of the voltage converter 10 are complementary. When a duty ratio of thesecond gate driving signal GD2 is close to 100%, the second gate drivingsignal GD2 has a max duty. If the second gate driving signal GD2 has themax duty, a duty ratio of the first gate driving signal GD1 is close to0%. That is, when the max duty occurs in the second gate driving signalGD2, the first transistor 12 may not be turned on, and the boostcapacitor CBST may not be charged. Accordingly, an abnormal operationthat the second gate driving signal GD2 fails to turn on the secondtransistor 13 may occur in the voltage converter 10.

FIG. 2 illustrates a voltage converter 100 according to an exampleembodiment of the inventive concepts, for solving the above-describedissues. Referring to FIG. 2, the voltage converter 100 includes firstand second transistors 120 and 130, first and second gate drivers 140and 150, a level shifter 160, a controller 180, a regulator 190, aninductor “L”, an output capacitor COUT, and a boost capacitor CBST.

The voltage converter 100 may convert an input voltage VIN of an inputnode NIN to an output voltage VOUT of an output node NOUT. For example,the voltage converter 100 may be a buck converter that steps down alevel of the input voltage VIN to output an output voltage VOUT.

The first and second transistors 120 and 130 may be connected in seriesbetween a ground node GND supplied with a ground voltage and the inputnode NIN. A node between the first and second transistors 120 and 130may be a switch node NSW. The inductor “L” is connected between theswitch node NSW and the output node NOUT. The output capacitor COUT isconnected between the output node NOUT and the ground node GND.

The first and second gate drivers 140 and 150 may control the first andsecond transistors 120 and 130, respectively, under control of thecontroller 180. The first gate driver 140 is biased by a power supplyvoltage VDD and the ground voltage. The first gate driver 140 may outputa first gate driving signal GD1 to control a gate (or a gate voltage) ofthe first transistor 120.

The second gate driver 150 is biased by a boost voltage VBST of a boostnode NBST and a switch voltage VSW of the switch node NSW. The secondgate driver 150 may output a second gate driving signal GD2 to control agate (or a gate voltage) of the second transistor 130.

The controller 180 may receive a clock signal CLK, the output voltageVOUT, and the switch voltage VSW. The controller 180 may control thefirst and second driving signals DRV1 and DRV2 in response to the clocksignal CLK, the output voltage VOUT, and/or the switch voltage VSW. Forexample, the controller 180 may control the first and second drivingsignals DRV1 and DRV2 such that the output voltage VOUT or the switchvoltage VSW is maintained at a target level.

The first driving signal DRV1 of the controller 180 is transmitted tothe first gate driver 140. The second driving signal DRV2 of thecontroller 180 is transmitted to the second gate driver 150 through thelevel shifter 160. The level shifter 160 may translate (e.g., increase)a level of the second driving signal DRV2 to a level defined by theboost voltage VBST and the switch voltage VSW.

The controller 180 may further receive the boost voltage VBST and apulse skip signal PSK. The controller 180 may generate control signalsCP in response to the clock signal CLK, the boost voltage VBST, theswitch voltage VSW, and the pulse skip signal PSK. The control signalsCP may be transmitted to the regulator 190 to control an operation ofthe regulator 190.

The pulse skip signal PSK may be received from an external device (e.g.,logic) that controls a pulse skip. If the voltage converter 100 iscontrolled to operate in a pulse skip mode, the pulse skip signal PSKmay be activated (e.g., to a high level). If the voltage converter 100exits from the pulse skip mode and a given time elapses, the pulse skipsignal PSK may be deactivated (for example, a low level).

The regulator 190 may receive the control signals CP from the controller180. The regulator 190 may further receive the input voltage VIN and theoutput voltage VOUT. The regulator 190 may control a voltage of theboost node NBST in response to the control signals CP, the input voltageVIN, and the output voltage VOUT. The boost capacitor CBST is connectedbetween the boost node NBST and the switch node NSW.

The regulator 190 may operate in at least three modes under control ofthe control signals CP. The at least three modes may include a normalmode, an input voltage pumping mode, and an output voltage pumping mode.In the normal mode, the regulator 190 may output the power supplyvoltage VDD to the boost node NBST.

In the input voltage pumping mode, the regulator 190 may output avoltage pumped from the input voltage VIN to the boost node NBST. In theoutput voltage pumping mode, the regulator 190 may output a voltagepumped from the output voltage VOUT to the boost node NBST. An operationof the regulator 190 will be described in detail later.

The first and second transistors 120 and 130, the first and second gatedrivers 140 and 150, the level shifter 160, the controller 180, and theregulator 190 may be implemented with a single chip 110. However,components included in the single chip 110 are not limited to the firstand second transistors 120 and 130, the first and second gate drivers140 and 150, the level shifter 160, the controller 180, and theregulator 190.

FIG. 3 is a flowchart illustrating an operating method of the voltageconverter 100 according to an example embodiment of the inventiveconcepts. Referring to FIGS. 2 and 3, in operation S110, the voltageconverter 100 determines whether the boost voltage VBST is insufficient.For example, when a difference between the boost voltage VBST and theswitch voltage VSW is lower than a reference voltage, the voltageconverter 100 may determine that the boost voltage VBST is insufficient.As another example, when the voltage converter 100 exits from the pulseskip mode, the voltage converter 100 may determine that the boostvoltage VBST is insufficient.

If the boost voltage VBST is insufficient, the voltage converter 100enters the output voltage pumping mode. In operation S120, the voltageconverter 100 may control the boost voltage VBST by pumping the outputvoltage VOUT. For example, the regulator 190 may control the boostvoltage VBST to be higher in level, by an amount of the power supplyvoltage VDD, than the output voltage VOUT.

The boost voltage VBST may be insufficient in two cases. For example,when the voltage converter 100 start to be powered, the boost voltageVBST may be insufficient. When the voltage converter 100 exits from thepulse skip mode, the boost voltage VBST may be insufficient.

In the case where the voltage converter 100 is used in a mobile deviceincluding a battery, the output voltage VOUT may be a voltage of thebattery. When power is not supplied to the voltage converter 100 or whenthe voltage converter 100 is in the pulse skip mode, the switch voltageVSW may gradually increase to the output voltage VOUT.

If the boost voltage VBST is pumped from the output voltage VOUT whenpower starts to be supplied to the voltage converter 100 or when thevoltage converter 100 exits from the pulse skip mode, then the boostvoltage VBST to be greater than the switch voltage VSW may be secured.Accordingly, an abnormal operation in which the second transistor 130 isnot turned on may be prevented or mitigated.

For example, if the boost voltage VBST is sufficient, the voltageconverter 100 may enter the normal mode. For example, in the normalmode, the voltage converter 100 may control the boost voltage VBSTdepending on operation S150, which will be described below.

If the boost voltage VBST is sufficient, operation S130 is performed. Inoperation S130, the voltage converter 100 may determine whether a maxduty occurs. For example, when a duty ratio of the second driving signalDRV2 is greater than a threshold value, the max duty may be determined.If the max duty is determined, the voltage converter 100 may enter aninput voltage pumping mode. In the input voltage pumping mode, operationS140 is performed.

In operation S140, the voltage converter 100 may control the boostvoltage VBST through pumping from the input voltage VIN. If the max dutyoccurs, in an operation period of the first and second transistors 120and 130, a time when the second transistor 130 is turned on is longerthan a time when the first transistor 120 is turned on.

When the second transistor 130 is turned on, the switch voltage VSW isthe same as the input voltage VIN. If the boost voltage VBST is pumpedfrom the input voltage VIN when the second transistor 130 is turned on,then the boost voltage VBST to be greater than the switch voltage VSWmay be secured. Accordingly, an abnormal operation in which the secondtransistor 130 is not turned on may be prevented or mitigated.

For example, if the voltage converter 100 does not have the max duty anylonger, the voltage converter 100 may enter the normal mode. Forexample, in the normal mode, the voltage converter 100 may control theboost voltage VBST depending on operation S150, which will be describedbelow.

If the boost voltage VBST is sufficient and the max duty is notdetermined, the voltage converter 100 may operate in the normal mode. Inthe normal mode, operation S150 is performed. In operation S150, theregulator 190 may output the power supply voltage VDD to the boost nodeNBST. When the first transistor 120 is turned on, the boost capacitorCBST may be charged to the power supply voltage VDD.

When the second transistor 130 is turned on, the boost voltage VBST maybe a voltage that corresponds to a sum of the switch voltage VSW (e.g.,the input voltage VIN) and a charging voltage of the boost capacitorCBST. Thus, the boost voltage VBST to be greater than the switch voltageVSW may be secured. Accordingly, an abnormal operation in which thesecond transistor 130 is not turned on may be prevented or mitigated.

FIG. 4 is a block diagram illustrating the controller 180 according toan example embodiment of the inventive concepts. Referring to FIG. 4,the controller 180 includes a pulse width modulator 181, a gate drivevoltage generator 183, a max duty detector 185, a boost voltage detector187, and a regulation signal generator 189.

The pulse width modulator 181 may receive the clock signal CLK and theoutput voltage VOUT. The pulse width modulator 181 may output a pulsewidth modulation signal PWM having a pulse width that varies dependingon a level of the output voltage VOUT. The pulse width modulation signalPWM is transmitted to the gate drive voltage generator 183.

The gate drive voltage generator 183 may output the first and seconddriving signals DRV1 and DRV2 in response to the pulse width modulationsignal PWM. For example, the gate drive voltage generator 183 mayincrease (or decrease) a high level interval or a low level interval ofthe first driving signal DRV1 or the second driving signal DRV2 as apulse width of the pulse width modulation signal PWM increases.

The first and second driving signals DRV1 and DRV2 may be complementary.If the high level interval of the first driving signal DRV1 increases(or the low level interval thereof decreases), the high level intervalof the second driving signal DRV2 may decrease (or the low levelinterval thereof may increase). Likewise, if the high level interval ofthe first driving signal DRV1 decreases (or the low level intervalthereof increases), the high level interval of the second driving signalDRV2 may increase (or the low level interval thereof may decrease).

The pulse width modulator 181 and the gate drive voltage generator 183may adjust lengths of high level intervals or low level intervals of thefirst and second driving signals DRV1 and DRV2 depending on a level ofthe output voltage VOUT. The output voltage VOUT may be controlled to atarget level by adjusting the first and second driving signals DRV1 andDRV2.

The max duty detector 185 receives the clock signal CLK and the firstdriving signal DRV1. The max duty detector 185 may determine whether thesecond driving signal DRV2 has the max duty in response to the clocksignal CLK and the first driving signal DRV1. The max duty detector 185may output the determination result as a max duty signal DMAX.

If the second driving signal DRV2 has the max duty, the max dutydetector 185 may activate the max duty signal DMAX (or may make the maxduty signal DMAX high). If the second driving signal DRV2 does not havethe max duty, the max duty detector 185 may deactivate the max dutysignal DMAX (or may make the max duty signal DMAX low).

The boost voltage detector 187 may receive the boost voltage VBST andthe switch voltage VSW. The boost voltage detector 187 may determinewhether a difference between the boost voltage VBST and the switchvoltage VSW is less than a reference voltage. If the difference is lessthan the reference voltage, the boost voltage detector 187 may activatea boost voltage signal DVBST (or may make the boost voltage signal DVBSTlow). If the difference is not less than the reference voltage, theboost voltage detector 187 may deactivate the boost voltage signal DVBST(or may make the boost voltage signal DVBST high).

The regulation signal generator 189 may receive the clock signal CLK,the max duty signal DMAX, the boost voltage signal DVBST, the pulse skipsignal PSK, and the second driving signal DRV2. The regulation signalgenerator 189 may control first to fourth control signals CP_S1 to CP_S4in response to the clock signal CLK, the max duty signal DMAX, the boostvoltage signal DVBST, the pulse skip signal PSK, and the second drivingsignal DRV2.

The first to fourth control signals CP_S1 to CP_S4 may be transmitted tothe regulator 190. The regulation signal generator 189 may allow theregulator 190 to operate in one of at least three modes including theinput voltage pumping mode, the output voltage pumping mode, and thenormal mode, by using the first to fourth control signals CP_S1 toCP_S4.

FIG. 5 illustrates an example of the max duty detector 185 according toan example embodiment of the inventive concepts. The max duty detector185 may determine the max duty of the second driving signal DRV2 inresponse to the clock signal CLK and the first driving signal DRV1.Referring to FIGS. 4 and 5, the max duty detector 185 includes first tothird blocks 185 a, 185 b, and 185 c and a flip-flop 185 d.

In an example embodiment, the max duty detector 185 may detect the maxduty of the second driving signal DRV2 from the first driving signalDRV1 based on a complementary characteristic of the first and seconddriving signals DRV1 and DRV2. However, the scope and spirit of theinventive concepts are not limited thereto. In some example embodiments,the max duty detector 185 may detect the max duty directly from thesecond driving signal DRV2.

The first block 185 a may periodically output a max duty detection pulseDMD for detecting the max duty of the second driving signal DRV2. Thefirst block 185 a may include a first delay 185 a 1, a first inverter185 a 2, and a first AND element 185 a 3.

The first delay 185 a 1 may delay the clock signal CLK to output adelayed clock signal CLKP. The first inverter 185 a 2 may invert theclock signal CLK to output an inverted clock signal CLKB. The first ANDelement 185 a 3 may perform an AND operation on the delayed clock signalCLKP and the inverted clock signal CLKB to output the max duty detectionpulse DMD.

The second block 185 b may output a reset signal RST representing thatthe second driving signal DRV2 does not have the max duty. The secondblock 185 b may include a second AND element 185 b 1, a second delay 185b 2, and a third AND element 185 b 3. The second AND element 185 b 1 mayoutput the result of performing an AND operation on the max dutydetection pulse DMD and the first driving signal DRV1 as a firstinternal signal A1.

The second delay 185 b 2 may delay the first internal signal A1 tooutput a second internal signal A2. The third AND element 185 b 3 mayoutput the result of performing an AND operation on the first and secondinternal signals A1 and A2 as the reset signal RST. The reset signal RSTmay be transmitted to a reset input of the flip-flop 185 d.

In an example embodiment, the second delay 185 b 2 and the third ANDelement 185 b 3 may prevent or mitigate the reset signal RST fromfluctuating when a level of the max duty detection pulse DMD or thefirst driving signal DRV1 is converted. In an anti-fluctuation system,the output of the second AND element 185 b 1 may be used as the resetsignal RST.

The third block 185 c may output a set signal SET representing that thesecond driving signal DRV2 has the max duty. The set signal SET may betransmitted to a set input of the flip-flop 185 d. The third block 185 cmay include a second inverter 185 c 1, a fourth AND element 185 c 2, athird delay 185 c 3, and a fifth AND element 185 c 4.

The second inverter 185 c 1 may invert the first driving signal DRV1 tooutput an inverted first driving signal DRV1B. The fourth AND element185 c 2 may output the result of performing an AND operation on the maxduty detection pulse DMD and the inverted first driving signal DRV1B asa third internal signal A3.

The third delay 185 c 3 may delay the third internal signal A3 to outputa fourth internal signal A4. The fifth AND element 185 c 4 may outputthe result of performing an AND operation on the third and fourthinternal signals A3 and A4 as the set signal SET. The output of theflip-flop 185 d may be set in response to the set signal SET and may bereset in response to the reset signal RST. The output of the flip-flop185 d may be the max duty signal DMAX. The flip-flop 185 d may include aset-reset flip-flop (SRFF).

In an example embodiment, the third delay 185 c 3 and the fifth ANDelement 185 c 4 may prevent or mitigate the set signal SET fromfluctuating when a level of the max duty detection pulse DMD or thefirst driving signal DRV1 is converted. In an anti-fluctuation system,the output of the fourth AND element 185 c 2 may be used as the setsignal SET.

FIG. 6 illustrates an example in which the max duty detection signal DMDis generated from the clock signal CLK, the inverted clock signal CLKB,and the delayed clock signal CLKP. Referring to FIGS. 2, 5, and 6, theinverted clock signal CLKB may have an inverted waveform of the clocksignal CLK. The delayed clock signal CLKP may have a waveform of theinverted clock signal CLKB delayed as much as a delay time DT.

The max duty detection pulse DMD may be generated through a logical ANDof the inverted clock signal CLKB and the delayed clock signal CLKP.Accordingly, the max duty detection pulse DMD has high levels inintervals in which the inverted clock signal CLKB and the delayed clocksignal CLKP all have a high level.

The max duty detection pulse DMD has low levels in intervals in which atleast one of the inverted clock signal CLKB and the delayed clock signalCLKP has a low level. The max duty detection pulse DMD is illustrated inFIG. 6 as first to fifth pulses P1 to P5 having a high levelperiodically. In an example embodiment, a delay amount of the firstdelay 185 a 1 may be adjusted to set a pulse width of the max dutydetection pulse DMD to a desired value.

FIG. 7 illustrates an example in which the second block 185 b generatesthe reset signal RST as a pulse width of the first driving signal DRV1changes. Referring to FIGS. 2, 5, and 7, the first to fifth pulses P1 toP5 are illustrated as the max duty detection pulse DMD. The pulse widthof the first driving signal DRV1 may gradually decrease. That is, thepulse width of the second driving signal DRV2 may gradually increase.

For example, the pulse width of the first driving signal DRV1 maygradually decrease with regard to the first to third pulses P1 to P3. Apulse of the first driving signal DRV1 may not be generated with regardto the fourth and fifth pulses P4 and P5. The second driving signal DRV2may have the max duty with regard to the fourth and fifth pulses P4 andP5.

The internal signal A1 may be generated by performing an AND operationon the max duty detection pulse DMD and the first driving signal DRV1.Accordingly, when the max duty detection pulse DMD and the first drivingsignal DRV1 all have a high level, the first internal signal A1 has ahigh level. When at least one of the max duty detection pulse DMD andthe first driving signal DRV1 has a low level, the first internal signalA1 has a low level.

The second internal signal A2 may be a signal generated by delaying thefirst internal signal A1. The reset signal RST is generated byperforming an AND operation on the first and second internal signals A1and A2. Accordingly, when the first and second internal signals A1 andA2 all have a high level, the reset signal RST may have a high level.

With regard to the first and second pulses P1 and P2, the first andsecond internal signals A1 and A2 have an interval in which high levelsthereof overlap with each other. Accordingly, the second block 185 b mayoutput (or activate) the reset signal RST with regard to the first andsecond pulses P1 and P2. That is, with regard to the first and secondpulses P1 and P2, the second block 185 b may determine that the seconddriving signal DRV2 does not have the max duty.

The max duty signal DMAX, which is the output of the flip-flop 185 d,may be periodically reset in response to the activated reset signal RST.For example, with regard to the first and second pulses P1 and P2, theflip-flop 185 d may reset the max duty signal DMAX to a low level.

With regard to the third to fifth pulses P3 to A5, the first and secondinternal signals A1 and A2 do not have an interval in which high levelsthereof overlap with each other. Accordingly, with regard to the thirdto fifth pulses P3 to P5, the second block 185 b may not output (oractivate) the reset signal RST. For example, the second block 185 b maynot determine that the second driving signal DRV2 does not have the maxduty.

FIG. 8 illustrates an example in which the third block 185 c generatesthe set signal SET as a pulse width of the first driving signal DRV1changes. Referring to FIGS. 2, 5, and 8, the first to fifth pulses P1 toP5 are illustrated as the max duty detection pulse DMD. The pulse widthof the first driving signal DRV1 may gradually decrease. That is, thepulse width of the second driving signal DRV2 may gradually increase.

The inverted first driving signal DRV1B may be an inverted waveform ofthe first driving signal DRV1. The third internal signal A3 may begenerated by performing an AND operation on the max duty detection pulseDMD and the inverted first driving signal DRV1B. Accordingly, the thirdinternal signal A3 has high levels in intervals where the max dutydetection pulse DMD and the inverted first driving signal DRV1B all havehigh levels.

The fourth internal signal A4 may be a signal generated by delaying thethird internal signal A3. The set signal SET is generated by performingan AND operation on the third and fourth internal signals A3 and A4.Accordingly, the set signal SET may have high levels in intervals wherethe third and fourth internal signals A3 and A4 all have high levels.

With regard to the first and second pulses P1 and P2, the third internalsignal A3 does not have a high level. Accordingly, with regard to thefirst and second pulses P1 and P2, the third block 185 c may not output(or activate) the set signal SET. With regard to the third to fifthpulses P3 to P5, the third internal signal A3 has high levels.

With regard to the third to fifth pulses P3 to P5, the third and fourthinternal signals A3 and A4 have intervals in which high levels thereofoverlap with each other. Accordingly, with regard to the third to fifthpulses P3 to P5, the third block 185 c may output (or activate) the setsignal SET representing that the second driving signal DRV2 has the maxduty.

As the third block 185 c activates the set signal SET, the flip-flop 185d may activate the max duty signal DMAX to a high level. For example,with regard to the third to fifth pulses P3 to P5, the third block 185 cmay periodically set the max duty signal DMAX of the flip-flop 185 d toa high level.

The inventive concepts are not limited to the case that the max dutydetector 185 activates the max duty signal DMAX only when the seconddriving signal DRV2 completely has the max duty. In some exampleembodiments, the max duty detector 185 may activate the max duty signalDMAX when the duty ratio of the second driving signal DRV2 is greaterthan a threshold value. The threshold value may be determined byparameters of the voltage converter 100 that have high levels inintervals where the third and fourth internal signals A3 and A4 overlapwith each other.

As described above, if the duty ratio of the second driving signal DRV2(or a duty ratio of a low level of the first driving signal DRV1) isgreater than the threshold value, the max duty detector 185 may activatethe max duty signal DMAX to a high level. If the duty ratio of thesecond driving signal DRV2 is not greater than the threshold value, themax duty detector 185 may deactivate the max duty signal DMAX to a lowlevel. Accordingly, the max duty detector 185 may detect the max duty ofthe second driving signal DRV2.

FIG. 9 illustrates an example of the boost voltage detector 187according to an example embodiment of the inventive concepts. Referringto FIGS. 5 and 9, the boost voltage detector 187 includes first tofourth resistors 187 a to 187 d, a first comparator 187 e, a fifthresistor 187 f, and a second comparator 187 g.

The first and second resistors 187 a and 187 b may divide the boostvoltage VBST. A first voltage V1, which is the result obtained bydividing the boost voltage VBST by the first and second resistors 187 aand 187 b, may be transmitted to a positive input of the firstcomparator 187 e. The third and fourth resistors 187 c and 187 d maydivide the switch voltage VSW. A second voltage V2, which is the resultobtained by dividing the switch voltage VSW by the third and fourthresistors 187 c and 187 d, may be transmitted to a negative input of thefirst comparator 187 e.

In an example embodiment, a division ratio of the first and secondresistors 187 a and 187 b and a division ratio of the third and fourthresistors 187 c and 187 d may be the same. That is, a difference betweenthe first and second voltages V1 and V2 may be proportional to adifference between the boost voltage VBST and the switch voltage VSW.

The first comparator 187 e may compare the first voltage V1 and thesecond voltage V2. The first comparator 187 e may output a third voltageV3 that is proportional to a difference between the first voltage V1 andthe second voltage V2. The third voltage V3 may be proportional to adifference between the boost voltage VBST and the switch voltage VSW.The third voltage V3 may be transmitted to a positive input of thesecond comparator 187 g.

The fifth resistor 187 f may allow the third voltage V3 to be generatedat an output of the first comparator 187 e. The second comparator 187 gmay compare the third voltage V3 and a reference voltage VREF. If thethird voltage V3 is greater than the reference voltage VREF, that is, ifa difference between the boost voltage VBST and the switch voltage VSW(or a voltage proportional to the difference) is greater than thereference voltage VREF, the second comparator 187 g may deactivate theboost voltage signal DVBST (or may make the boost voltage signal DVBSThigh).

If the third voltage V3 is not greater than the reference voltage VREF,that is, if the difference between the boost voltage VBST and the switchvoltage VSW (or the voltage proportional to the difference) is notgreater than the reference voltage VREF, the second comparator 187 g mayactivate the boost voltage signal DVBST (or may make the boost voltagesignal DVBST low).

If the boost voltage signal DVBST is deactivated (e.g., to a highlevel), the boost voltage VBST is determined as being sufficientlygreater than the switch voltage VSW. For example, the boost voltage VBSTis determined to be sufficient if the second gate driver 150 drives thesecond transistor 130 to be turned on.

If the boost voltage signal DVBST is activated (e.g., to a low level),the boost voltage VBST is determined as being not sufficiently greaterthan the switch voltage VSW. For example, the boost voltage VBST isdetermined to be insufficient if the second gate driver 150 fails todrive the second transistor 130 to be turned on.

FIG. 10 illustrates an example of the regulation signal generator 189according to an example embodiment of the inventive concepts. Referringto FIGS. 2, 5, and 10, the regulation signal generator 189 includes astatus determination block 189 a and a regulation signal generationblock 189 b. The status determination block 189 a may determine thestatus of the voltage converter 100 in response to the max duty signalDMAX, the boost voltage signal DVBST, and the pulse skip signal PSK.

The status determination block 189 a may control first and secondsignals S1 and S2 based on the determined status. For example, if adifference between the boost voltage VBST and the switch voltage VSW isless than a reference voltage or if it is determined that the voltageconverter 100 exist from the pulse skip mode, and thus, the boostvoltage VBST is insufficient, the status determination block 189 a mayactivate the first signal S1 to a high level.

In the case where the boost voltage VBST is sufficient, the statusdetermination block 189 a may deactivate the first signal S1 to a lowlevel. If the boost voltage VBST is sufficient, but that the seconddriving signal DRV2 is determined to have the max duty (refer tooperation S130 of FIG. 3), the status determination block 189 a mayactivate the second signal S2 to a high level.

The status determination block 189 a includes a first statusdetermination inverter 189 a_1, a first status determination AND element189 a_2, a status determination NOR element 189 a_3, a second statusdetermination inverter 189 a_4, and a second status determination ANDelement 189 a_5. The first status determination inverter 189 a_1 mayinvert and output the boost voltage signal DVBST.

The first status determination AND element 189 a_2 may output a logicalproduct of the boost voltage signal DVBST and the pulse skip signal PSK.The status determination NOR element 189 a_3 may output logical NOR ofan output of the first status determination inverter 189 a_1 and anoutput of the first status determination AND element 189 a_2.

The second status determination inverter 189 a_4 may invert the outputof the status determination NOR element 189 a_3 to output the firstsignal S1. The second status determination AND element 189 a_5 mayoutput a logical product of the max duty signal DMAX and the output ofthe status determination NOR element 189 a_3 to output the second signalS2.

If the boost voltage signal DVBST has a low level (e.g., the boostvoltage VBST is not sufficiently high) or the pulse skip signal PSK hasa high level (e.g., if the voltage converter 100 exits from the pulseskip mode), the status determination block 189 a may determine that theboost voltage VBST is insufficient (refer to operation S110 of FIG. 3).The first signal S1 may have values of Table 1 depending on the boostvoltage signal DVBST and the pulse skip signal PSK.

TABLE 1 Boost voltage signal Pulse skip signal First signal (DVBST)(PSK) (S1) 1 (sufficient) 1 (pulse skip mode) 1 (activation) 1(sufficient) 0 0 (deactivation) 0 (insufficient) 1 (pulse skip mode) 1(activation) 0 (insufficient) 0 1 (activation)

If the boost voltage VBST is sufficient, but the second driving signalDRV2 has the max duty, the status determination block 189 a may activatethe second signal S2. The second signal S2 may have values of Table 2depending on the first signal S1 and the max duty signal DMAX.

TABLE 2 First signal (S1) Max duty signal (DMAX) Second signal (S2) 0(deactivation) 1 (max duty) 1 0 (deactivation) 0 0 1 (activation) 1 (maxduty) 0 1 (activation) 0 0

The regulation signal generation block 189 b may control the first tofourth control signals CP₁₃ S1 to CP₁₃ S4 in response to the first andsecond signals S1 and S2, the clock signal CLK, and the second drivingsignal DRV2. The regulation signal generation block 189 b includes afirst regulation inverter 189 b_1, a regulation NAND element 189 b_2, asecond regulation inverter 189 b_3, a first regulation AND element 189b_4, a regulation NOR element 189 b_5, a second regulation AND element189 b_6, a regulation OR element 189 b_7, a third regulation inverter189 b_8, a regulation NOR element 189 b_9, and a fourth regulationinverter 189 b_10.

The first regulation inverter 189 b_1 may invert the clock signal CLK tooutput the inverted clock signal CLKB. The regulation NAND element 189b_2 may output the result of performing a NAND operation on the seconddriving signal DRV2, the inverted clock signal CLKB, and the secondsignal S2 as a third signal S3.

The second regulation inverter 189 b_3 may invert the third signal S3 tooutput the second control signal CP_S2. The first regulation AND element189 b_4 may output the result of performing an AND operation on thethird signal S3, the clock signal CLK, and the second signal S2 as afourth signal S4. The regulation NOR element 189 b_5 may output theresult of performing a NOR operation on the second signal S2 and thefirst signal S1 as a fifth signal S5.

The second regulation AND element 189 b_6 may output the result ofperforming an AND operation on the first signal S1 and the clock signalCLK as a sixth signal S6. The regulation OR element 189 b_7 may outputthe result of performing an OR operation on the fourth signal S4, thefifth signal S5, and the sixth signal S6 as the first control signalCP_S1.

The third regulation inverter 189 b_8 may invert the first signal S1 tooutput a seventh signal S7. The regulation NOR element 189 b_9 mayoutput the result of performing a NOR operation on the seventh signal S7and the sixth signal S6 as the fourth control signal CP_S4. The fourthregulation inverter 189 b_10 may invert the first signal S1 to outputthe third control signal CP_S3. The first to fourth control signalsCP_S1 to CP_S4 may be transmitted to the regulator 190.

FIG. 11 illustrates an example of the regulator 190 according to anexample embodiment of the inventive concepts. Referring to FIGS. 2 and11, the regulator 190 includes first to fourth transistors 191 a to 194a, first to fourth drivers 191 b to 194 b, a level shifter 192 c, firstto third diodes 195 a to 195 c, and a capacitor 196.

The first and second transistors 191 a and 192 a are connected in seriesbetween the ground node GND and the input node NIN. A node between thefirst and second transistors 191 a and 192 a may be a low node LN. Agate voltage of the first transistor 191 a is controlled by the firstdriver 191 b. A gate voltage of the second transistor 192 a iscontrolled by the second driver 192 b.

The third and fourth transistors 193 a and 194 a are connected in seriesbetween the ground node GND and the output node NOUT. A gate voltage ofthe third transistor 193 a is controlled by the third driver 193 b. Agate voltage of the fourth transistor 194 a is controlled by the fourthdriver 194 b.

A cathode of the first diode 195 a is connected to the low node LN. Ananode of the first diode 195 a is connected to a node between the thirdand fourth transistors 193 a and 194 a. The second and third diodes 195b and 195 c are connected in series between a power node, to which thepower supply voltage VDD is supplied, and the boost node NBST. A nodebetween the second and third diodes 195 b and 195 c may be a high nodeHN.

The first driver 191 b is biased by the power supply voltage VDD and theground voltage of the ground node GND. The first driver 191 b mayoperate in response to the first control signal CP_S1. The second driver192 b is biased by a high boost voltage VBST_H of the high node HN and alow boost voltage VBST_L of the low node LN.

The second driver 192 b may be controlled according to a signal that isgenerated by translating a level of the second control signal CP_S2 atthe level shifter 192 c. For example, the level shifter 192 c maytranslate (e.g., increase) a level of the second control signal CP_S2 toa level defined by the high boost voltage VBST_H and the low boostvoltage VBST_L.

The third driver 193 b is biased by the power supply voltage VDD and theground voltage. The third driver 193 b may be controlled by the thirdcontrol signal CP_S3. The fourth driver 194 b is biased by the powersupply voltage VDD and the ground voltage. The fourth driver 194 b iscontrolled by the fourth control signal CP_S4. The capacitor 196 isconnected between the high node HN and the low node LN.

FIG. 12 illustrates an example of signals associated with the regulationsignal generation block 189 b when the first signal S1 and the secondsignal S2 are deactivated. That is, FIG. 12 illustrates signals when thevoltage converter 100 is at a normal state. In other words, FIG. 12illustrates signals when a difference between the boost voltage and theswitch voltage is not less than a reference voltage, when the voltageconverter does not exit from a pulse skip mode, and when a duty ratio ofthe gate voltage of the second transistor is not greater than athreshold value. Referring to FIGS. 2, 10, and 12, the clock signal CLKand the second driving signal DRV2 are illustrated.

The third signal S3 has a low level when the second signal S2 is at ahigh level (e.g., is activated), the clock signal CLK is at a low level,and the second driving signal DRV2 is at a high level. Because FIG. 12assumes that the second signal S2 is at a low level (e.g., isdeactivated), the third signal S3 is fixed to a high level.

The fourth signal S4 has a high level when the third signal S3, theclock signal CLK, and the second signal S2 all are at a high level.Because FIG. 12 assumes that the second signal S2 is at a low level(e.g., is deactivated), the fourth signal S4 is fixed to a low level.The fifth signal S5 has a high level when both the first and secondsignals S1 and S2 are at a low level. Because FIG. 12 assumes that boththe first signal S1 and the second signal S2 are at a low level, thefifth signal S5 is fixed to a high level.

The sixth signal S6 has a high level when both the first signal S1 andthe clock signal CLK are at a high level. Because FIG. 12 assumes thatthe first signal S1 is at a low level, the sixth signal S6 is fixed to alow level. The first control signal CP_S1 has a low level only when allthe fourth to sixth signals S4 to S6 are at a low level. Because FIG. 12assumes that the fifth signal S5 is at a high level, the first controlsignal CP_S1 is fixed to a high level.

The second control signal CP_S2 may be an inverted version of the thirdsignal S3. Because the third signal S3 is at a high level, the secondcontrol signal CP_S2 is fixed to a low level. The third control signalCP_S3 may be an inverted version of the first signal S1. Because FIG. 12assumes that the first signal S1 is at a low level, the third controlsignal CP_S3 is fixed to a high level.

The fourth control signal CP_S4 has a high level only when both thesixth and seventh signals S6 and S7 are at a low level. The sixth signalS6 may be an inverted version of the first signal S1. Accordingly, thefourth control signal CP_S4 has a high level only when the first signalS1 is at a high level and the sixth signal S6 is at a low level. Becausethe first signal S1 has a low level, the fourth control signal CP_S4 isfixed to a low level.

FIG. 13 illustrates how the regulator 190 is controlled by signals ofFIG. 12. Referring to FIGS. 2, 12, and 13, because the second and fourthcontrol signals CP_S2 and CP_S4 are fixed to a low level, the second andfourth transistors 192 a and 194 a maintain a turn-off state. Becausethe first and third control signals CP_S1 and CPS_3 are fixed to a highlevel, the first and third transistors 191 a and 193 a maintain aturn-on state.

A voltage of the low node LN is a ground voltage. The power supplyvoltage VDD is supplied to the boost node NBST through the second andthird diodes 195 b and 195 c. While the first transistor 120 is turnedon, the boost capacitor CBST is charged by the power supply voltage VDDoutput from the regulator 190.

At timing when the first transistor 120 is turned off and the secondtransistor 130 is turned on, the boost voltage VBST may be greater thanthe switch voltage VSW by a voltage (e.g., the power supply voltage VDD)charged in the boost capacitor CBST. Accordingly, the second gate driver150 may turn on the second transistor 130 based on the boost voltageVBST.

FIG. 14 illustrates an example of signals associated with the regulationsignal generation block 189 b when the first signal S1 is activated andthe second signal S2 are deactivated. That is, FIG. 14 illustratessignals that are controlled to the output voltage pumping mode due tothe insufficiency of the boost voltage VBST in the voltage converter100. Referring to FIGS. 2, 10, and 14, the clock signal CLK and thesecond driving signal DRV2 are illustrated.

The third signal S3 has a low level when the second signal S2 is at ahigh level (e.g., is activated), the clock signal CLK is at a low level,and the second driving signal DRV2 is at a high level. Because FIG. 14assumes that the second signal S2 is at a low level (e.g., isdeactivated), the third signal S3 is fixed to a high level.

The fourth signal S4 has a high level when the third signal S3, theclock signal CLK, and the second signal S2 all are at a high level.Because FIG. 14 assumes that the second signal S2 is at a low level(e.g., is deactivated), the fourth signal S4 is fixed to a low level.The fifth signal S5 has a high level when both the first signal S1 andthe second signal S2 are at a low level. Because FIG. 14 assumes thatthe first signal S1 is at a high level, the fifth signal S5 is fixed toa low level.

The sixth signal S6 has a high level when both the first signal S1 andthe clock signal CLK are at a high level. Because FIG. 14 assumes thatthe first signal S1 is at a high level, the sixth signal S6 may have thesame waveform as the clock signal CLK. The first control signal CP_S1has a low level only when all the fourth to sixth signals S4 to S6 areat a low level. In FIG. 14, because the fourth and fifth signals S4 andS5 are fixed to a low level, the first control signal CP_S1 has the samewaveform as the sixth signal S6.

The second control signal CP_S2 may be an inverted version of the thirdsignal S3. In FIG. 14, because the third signal S3 is at a high level,the second control signal CP_S2 is fixed to a low level. The thirdcontrol signal CP_S3 may be an inverted version of the first signal S1.Because FIG. 14 assumes that the first signal S1 is at a high level, thethird control signal CP_S3 is fixed to a low level.

The fourth control signal CP_S4 has a high level only when the firstsignal S1 is at a high level and the sixth signal S6 is at a low level.Because FIG. 14 assumes that the first signal S1 is at a high level andthe sixth signal S6 switches between a high level and a low level, thefourth control signal CP_S4 has an inverted waveform of the sixth signalS6. The fourth control signal CP_S4 may be complementary to the firstcontrol signal CP_S1.

FIG. 15 illustrates how the regulator 190 is controlled by signals ofFIG. 14. Referring to FIGS. 2, 14, and 15, because the second and thirdcontrol signals CP_S2 and CP_S3 are fixed to a low level, the second andthird transistors 192 a and 193 a maintain a turn-off state. Asillustrated by an arrow, each of the first and fourth control signalsCP_S1 and CP_S4 may switch between a high level and a low level and maytransmit a voltage pumped from the output voltage VOUT to the boost nodeNBST.

When the first transistor 191 a is turned on and the fourth transistor194 a is turned off, the capacitor 196 is charged with the power supplyvoltage VDD transmitted through the second diode 195 b. When the firsttransistor 191 a is turned off and the fourth transistor 194 a is turnedon, a voltage of the high node HN increases to a voltage correspondingto a sum of the output voltage VOUT and a voltage (e.g., the powersupply voltage VDD) charged in the capacitor 196. That is, a voltagepumped from the output voltage VOUT by an amount as much as the powersupply voltage VDD is transmitted to the boost node NBST.

FIG. 16 illustrates an example of signals associated with the regulationsignal generation block 189 b when the first signal S1 is deactivatedand the second signal S2 are activated. That is, FIG. 16 illustratessignals that are controlled to the input voltage pumping mode when themax duty occurs in the voltage converter 100. Referring to FIGS. 2, 10,and 16, the clock signal CLK and the second driving signal DRV2 areillustrated.

The third signal S3 has a low level when the second signal S2 is at ahigh level (e.g., is activated), the clock signal CLK is at a low level,and the second driving signal DRV2 is at a high level. Because FIG. 16assumes that the second signal S2 is at a high level (e.g., isactivated), the third signal S3 has low levels in intervals where theclock signal CLK is at a low level and the second driving signal DRV2 isat a high level. In the remaining intervals, the third signal S3 has ahigh level.

The fourth signal S4 has a high level when the third signal S3, theclock signal CLK, and the second signal S2 all are at a high level.Because FIG. 16 assumes that the second signal S2 is at a high level(e.g., is activated), the fourth signal S4 has high levels in intervalswhere the third signal S3 and the clock signal CLK are at a high level.In the remaining intervals, the fourth signal S4 has low levels.

The fifth signal S5 has a high level when the first and second signalsS1 and S2 all are at a low level. Because FIG. 16 assumes that thesecond signal S2 is at a high level, the fifth signal S5 is fixed to alow level. The sixth signal S6 has a high level when the first signal S1and the clock signal CLK all are at a high level. Because FIG. 16assumes that the first signal S1 is at a low level, the sixth signal S6is fixed to a low level.

The first control signal CP_S1 has a low level only when the fourth tosixth signals S4 to S6 all are at a low level. Because FIG. 16 assumesthat the fifth and sixth signals S5 and S6 are fixed to a low level, thefirst control signal CP_S1 has the same waveform as the fourth signalS4. The second control signal CP_S2 may be an inverted version of thethird signal S3.

The third control signal CP_S3 may be an inverted version of the firstsignal S1. Because FIG. 16 assumes that the first signal S1 is at a lowlevel, the third control signal CP_S3 is fixed to a high level. Thefourth control signal CP_S4 has a high level only when the first signalS1 is at a high level and the sixth signal S6 is at a low level. BecauseFIG. 16 assumes that the first signal S1 is at a low level, the fourthcontrol signal CP_S4 is fixed to a low level.

The first and second control signals CP_S1 and CP_S2 may becomplementary in intervals where the second driving signal DRV2 is at ahigh level. For example, in intervals where the second driving signalDRV2 is at a high level, if the first control signal CP_S1 is at a highlevel, the second control signal CP_S2 may be at a low level.

In intervals where the second driving signal DRV2 is at a high level, ifthe first control signal CP_S1 is at a low level, the second controlsignal CP_S2 may be at a high level. The first and second controlsignals CP_S1 and CP_S2 may have low levels in intervals where thesecond driving signal DRV2 is at a low level.

FIG. 17 illustrates how the regulator 190 is controlled by signals ofFIG. 16. Referring to FIGS. 2, 16, and 17, since the fourth controlsignal CP_S4 is fixed to a low level, the fourth transistor 194 amaintains a turn-off state. Because the third control signal CP_S3 isfixed to a high level, the third transistor 193 a maintains a turn-onstate.

As illustrated by an arrow, each of the first and second control signalsCP_S1 and CP_S2 may switch between a high level and a low level inintervals where the second driving signal DRV2 is at a high level andmay transmit a voltage pumped from the input voltage VIN to the boostnode NBST. When the first transistor 191 a is turned on and the secondtransistor 192 a is turned off, the capacitor 196 is charged with thepower supply voltage VDD transmitted through the second diode 195 b.

When the first transistor 191 a is turned off and the second transistor192 a is turned on, a voltage of the high node HN increases to a voltagecorresponding to a sum of a voltage of the high node HN and a voltage(e.g., the power supply voltage VDD) charged in the capacitor 196. Thatis, a voltage pumped from the input voltage VIN by an amount as much asthe power supply voltage VDD is transmitted to the boost node NBST.

FIG. 18 illustrates a voltage converter 200 according to an exampleembodiment of the inventive concepts. Referring to FIG. 18, the voltageconverter 200 includes first and second transistors 220 and 230, firstand second gate drivers 240 and 250, a level shifter 260, a controller280, a regulator 290, an inductor “L”, an input capacitor CIN, an outputcapacitor COUT, and a boost capacitor CBST.

The voltage converter 200 may convert an input voltage VIN of an inputnode NIN to an output voltage VOUT of an output node NOUT. For example,the voltage converter 200 may be a boost converter that steps up a levelof the input voltage VIN to output the output voltage VOUT.

The first and second transistors 220 and 230 may be connected in seriesbetween a ground node GND supplied with a ground voltage and the outputnode NOUT. A node between the first and second input transistors 120 and130 may be a switch node NSW. The inductor “L” is connected between theswitch node NSW and the input node NIN. The input capacitor CIN isconnected between the input node NIN and the ground node GND.

The boost capacitor CBST is connected between the switch node NSW andthe boost node NBST. The output capacitor COUT is connected between theoutput node NOUT and the ground node GND. The first and secondtransistors 220 and 230, the first and second gate drivers 240 and 250,the level shifter 260, the controller 280, and the regulator 290 are thesame as described with reference to FIG. 2, and thus, a descriptionthereof will not be repeated here.

The voltage converter 200 may enter the input voltage pumping mode whenthe boost voltage VBST is insufficient. The voltage converter 200 mayenter the output voltage pumping mode when the second driving signalDRV2 has the max duty. The regulator 290 may have the same structure ofFIG. 11 except that the input node NIN and the output node NOUT areexchanged. The controller 280 may have the same structure as describedwith reference to FIGS. 4 to 10.

According to an example embodiment of the inventive concepts, thevoltage converter 100 or 200 in which switching transistors may beimplemented with NMOS transistors. Because PMOS transistors are notused, the size of the voltage converter 100 or 200 may be reduced. Byconfiguring the regulator 190 or 290 to operate in at least three modesincluding the normal mode, the output voltage pumping mode, and theinput voltage pumping mode, the second transistor 130 or 230 can besecurely turned on at all times. Accordingly, the voltage converter 100or 200 with improved reliability can be implemented.

In the above-described example embodiments, components according toexample embodiments of the inventive concepts are referred to by usingthe term “block”. The “block” may be implemented with various hardwaredevices, such as an integrated circuit, an application specific IC(ASCI), a field programmable gate array (FPGA), and a complexprogrammable logic device (CPLD), software, such as firmware andapplications driven in hardware devices, or a combination of a hardwaredevice and software. Also, “block” may include circuits or intellectualproperty (IP) implemented with semiconductor devices.

According to the inventive concepts, a voltage converter adjusts a gatevoltage of a switching transistor such that the switching transistor isturned on according to a change in environment. Accordingly, the voltageconverter with improved reliability and/or an operating method thereofmay be provided.

While the inventive concepts have been described with reference toexample embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the inventive concepts. Therefore, itshould be understood that the above example embodiments are notlimiting, but illustrative.

What is claimed is:
 1. A voltage converter comprising: an inductorconnected between an output node and a switch node; a capacitorconnected between the output node and a ground node; a first transistorconnected between the switch node and the ground node; a secondtransistor connected between the switch node and an input node; a boostcapacitor connected between the switch node and a boost node; a firstdriver configured to drive a gate voltage of the first transistor basedon a ground voltage of the ground node and a power supply voltage of apower node; a second driver configured to drive a gate voltage of thesecond transistor based on a switch voltage of the switch node and aboost voltage of the boost node and; and a regulator configured tocontrol the boost voltage by selecting one of two or more modesdepending on a status of the voltage converter, the two or more modesincluding a first mode of pumping from an input voltage of the inputnode to generate the boost voltage, a second mode of pumping from anoutput voltage of the output node to generate the boost voltage, and athird mode of outputting of the power supply voltage as the boostvoltage.
 2. The voltage converter of claim 1, wherein the regulator isfurther configured to pump an output voltage of the output node togenerate the boost voltage if a difference between the boost voltage andthe switch voltage is less than a reference voltage.
 3. The voltageconverter of claim 1, wherein the regulator is further configured topump an output voltage of the output node to generate the boost voltageif the voltage converter exits from a pulse skip mode.
 4. The voltageconverter of claim 1, wherein the regulator is further configured topump an input voltage of the input node to generate the boost voltage ifa duty ratio of the gate voltage of the second transistor is greaterthan a threshold value.
 5. The voltage converter of claim 4, wherein theregulator is further configured to pump while the gate voltage of thesecond transistor is at a high level.
 6. The voltage converter of claim1, wherein the regulator is further configured to charge the boostcapacitor with the power supply voltage of the power node while thefirst transistor is turned on if a difference between the boost voltageand the switch voltage is not less than a reference voltage, the voltageconverter does not exit from a pulse skip mode, and a duty ratio of thegate voltage of the second transistor is not greater than a thresholdvalue.
 7. The voltage converter of claim 1, wherein the regulator isfurther configured to maintain the boost voltage of the boost node to begreater than the switch voltage of the switch node.
 8. The voltageconverter of claim 1, further comprising: a gate drive signal generatorconfigured to output a first driving signal to the first driver andoutput a second driving signal to the second driver; a max duty detectorconfigured to output a max duty signal based on a clock signal and thefirst driving signal if a duty ratio of the gate voltage of the secondtransistor is greater than a threshold value; a boost voltage detectorconfigured to output a boost voltage signal based one the boost voltageand the switch voltage if a difference between the boost voltage and theswitch voltage is less than a reference voltage; and a regulation signalgenerator configured to output first to fourth control signals to theregulator based on the max duty signal, the boost voltage signal, theclock signal, the second driving signal, and a pulse skip signal.
 9. Thevoltage converter of claim 8, wherein the max duty detector includes: afirst block configured to output a logical product of a delayed signalof the clock signal and an inverted signal of the clock signal as a maxduty detection pulse; a second block configured to produce a logicalproduct of the max duty detection pulse and the first driving signal asa first signal and output a logical product of the first signal and adelayed signal of the first signal as a reset signal; a third blockconfigured to produce a logical product of an inverted signal of thefirst driving signal and the max duty detection pulse as a second signaland output a logical product of the second signal and a delayed signalof the second signal as a set signal; and a flip-flop configured tooutput the max duty signal based on the reset signal and the set signal.10. The voltage converter of claim 8, wherein the max duty detector isconfigured to check a duty ratio of the first driving signalperiodically and activate the max duty signal if the duty ratio of thefirst driving signal is greater than the threshold value.
 11. Thevoltage converter of claim 8, wherein the boost voltage detectorincludes: first and second resistors configured to output a firstvoltage by dividing the boost voltage; third and fourth resistorsconfigured to output a second voltage by dividing the switch voltage; afirst comparator configured to output a difference between the firstvoltage and the second voltage as a third voltage; and a secondcomparator configured to output a difference between the third voltageand a reference voltage as the boost voltage signal.
 12. The voltageconverter of claim 8, wherein the regulation signal generator includes astatus determination block configured to: deactivate a first statussignal if the boost voltage signal and the pulse skip signal aredeactivated, and otherwise activate the first status signal; andactivate a second status signal if the first status signal isdeactivated and the max duty signal is activated, and otherwiseinactivate the second status signal.
 13. The voltage converter of claim12, wherein the regulation signal generator further includes a driveblock configured to: control the first to fourth control signals suchthat the regulator charges the power supply voltage in the boostcapacitor while the second driving signal is at a high level if thefirst and second status signals are deactivated.
 14. The voltageconverter of claim 13, wherein the drive block is further configured tocontrol the first to fourth control signals such that the regulatorpumps an output voltage of the output node to generate the boost voltageif the first status signal is activated and the second status signal isdeactivated.
 15. The voltage converter of claim 13, wherein the driveblock is further configured to control the first to fourth controlsignals such that the regulator pumps an input voltage of the input nodeto generate the boost voltage if the first status signal is deactivatedand the second status signal is activated.
 16. A voltage convertercomprising: an inductor connected between an input node and a switchnode; a first capacitor connected between the input node and a groundnode; a first transistor connected between the switch node and theground node; a second transistor connected between the switch node andan output node; a boost capacitor connected between the switch node anda boost node; a second capacitor connected between the output node andthe ground node; a first driver configured to drive a gate voltage ofthe first transistor; a second driver configured to drive a gate voltageof the second transistor depending on a boost voltage of the boost nodeand a switch voltage of the switch node; and a regulator configured tocontrol the boost voltage by selecting one of two or more modesdepending on a status of the voltage converter, the two or more modesincluding a first mode of pumping from an input voltage of the inputnode to generate the boost voltage, a second mode of pumping from anoutput voltage of the output node to generate the boost voltage, and athird mode of outputting of a power supply voltage as the boost voltage.17. The voltage converter of claim 16, wherein the status of the voltageconverter includes a first state where the boost voltage is not higher,by an amount of a reference value, than the switch voltage, a secondstate where the voltage converter exits from a pulse skip mode, and athird state where a duty ratio of the gate voltage of the secondtransistor is greater than a threshold value.